Nanodiamonds are rapidly emerging as promising carriers for next-generation therapeutics and drug delivery. However, developing future nanoscale devices and arrays that harness these nanoparticles will require unrealized spatial control. Furthermore, single-cell in vitro transfection methods lack an instrument that simultaneously offers the advantages of having nanoscale dimensions and control and continuous delivery via microfluidic components. To address this, two modes of controlled delivery of functionalized diamond nanoparticles are demonstrated using a broadly applicable nanofountain probe, a tool for direct-write nanopatterning with sub-100-nm resolution and direct in vitro single-cell injection. This study demonstrates the versatility of the nanofountain probe as a tool for high-fidelity delivery of functionalized nanodiamonds and other agents in nanomanufacturing and single-cell biological studies. These initial demonstrations of controlled delivery open the door to future studies examining the nanofountain probe's potential in delivering specific doses of DNA, viruses, and other therapeutically relevant biomolecules.

Researchers in the US have created a 'fountain pen' probe that can pattern nanodiamonds at high resolution and inject them into single cells. The probe could be used as a research and development tool for creating nanodiamond devices and exploring the effect of single cells carrying medical drugs.

Horacio Espinosa and others at Northwestern University in Evanston, US, have created a tool that they say offers more control over nanodiamond placement. It consists of the probe of an atomic force microscope that has been modified to house a reservoir filled with an 'ink' of nanodiamonds in solution. 'It's just like a fountain pen,' said Owen Loh, a member of the group.

Such nanofountain probes have been employed for placement of nanoparticles before, but never with nanodiamonds. In one mode, the Northwestern group's probe can pattern nanodiamonds onto a substrate with a resolution better than 100nm, three orders of magnitude finer than previously achievable. Loh told Chemistry World this ability could help seed the growth of nanodiamond thin films. In the past, nanodiamond thin films have been shown, for example, to prevent the re-growth of tumours when combined with anti-cancer drugs and implanted into the human body.

In a second mode, the probe can inject nanodiamonds into single cells. Until now it had only been possible to test nanodiamond drug delivery on populations of cells, and Loh said that the potential for more precise application will help scientists understand how drug-laden cells interact with their neighbours.

The group is presently collaborating with biologists and focusing on how to exploit the benefits of single-cell injection. 'The key part is that [both modes] are in the same tool, so researchers only need to familiarise themselves with one tool,' Loh added.